Multiple telephony



' E. RUHMER.

MULTIPLE TELEPHONY.

APPLICATION FILED APR.4. 19H. RENEWED FEB. 4.19:9.

Patented Oct. 19, 1920.

Q N N% 5% 3% ai g 53 M- INVENTOR 4W M M ATTORNEYS WITNESSES g/ %z UNITEDSTATES PATENT OFFICE.

ERNST BUHMEB,

0F BERLIN, GERMANY.

MULTIPLE TELEPHONY.

Application filed April 4, 1911, Serial No.

To all whom it may concern:

Be it known that I, ERNST Romans, engineer, a subject of the GermanEmperor, residing at Berlin, 248 Friedrichstrasse, in the Empire ofGermany, have invented new and useful Improvements in or Relating toMultiple Telephon for which application has been made in rance April 5,1910.

This invention relates to a method by means of which it is possible totransmit simultaneously several telephonic messages by one and the samewire.

For transmitting conversations, as in wireless telephony by means ofelectric waves, alternating currents of high frequency and of differentfrequency are used which are superposed on the line and are separatedonly at the receiving station where they act on different oscillatorycircuits tuned with corresponding oscillatory transmission circuitscommunicating with the receiving apparatus.

In this method a comparatively loose coupling is used for connecting thetransmission line to the different receiving circuits, as well as thelatter to each other, for the urpose of obtaining a perfect separationof the difl'erent conversations and thus for avoiding any possibility ofhearing unintentionally even the strongest of the latter,

which, more particularly in a case of a large number of simultaneoustransmissions, mi ht have a very awkward effect.

everal arrangements according to this invention are illustrated by wayof example in the accompanying drawings.

In the drawing,

Figure 1 is a diagrammatic view representing the transmitting andreceiving stations with independent sources of high frequency currentsat each transmitting station.

Fig. 2 represents diagrammatically a modified form of my improvedsystem.

Fig. 3 shows a combined sending and receiving station embodying myinvention.

In Fig. 1, A B C A B C are respectively the corresponding transmittingan receivin stations.

In or or to produce high frequency currents, a known high frequencygenerator is used here, for instance, a generator of electric wavescomprising an electric are 9 with an oscillating circuit 0 I placed inparallel.

The different oscillatory circuits are adspeciflcation of LettersPatent.

618,871. Renewed. February 4, 1919. Serial No.

Patented Oct. 19, 1920.

'usted to different numbers of oscillations lay a suitable choice of thecapacity a and of the self-induction Z.

The intensity ,of the rents produced inthese circuits is influence bytalking microphones m, which in some cases are in series with batteriesb, b',, b',, b or b respectively. Either the supply current, or the highfrequency current of the oscillatory circuit can be affected at will.

A changefin the coupling between the emission circuit and the line, isequivalent to a change of intensity of thehigh frequency current passingthrough the cirhigh frequency curcuits.

Generally speaking, any methods can be used, provided that themicrophone of a certain emitting station cannot affect the alternatingcurrents passing into the common line and emitted by other stations.There are receiving installations corresponding to the emission stationsthus arranged.

In the drawing A B are oscillatory circuits tuned to the periods of theoscillatory circuits of'the corresponding emission stations A 13. Theyact on the different receiving telephones t owing to the insertion of adetector d, as in wireless tele hony with electric waves. At C the transormation is effected direct, without a detector, by means of a telephoneto with Foucault currents.

The transmission" of different talking currents is effected by thecommon line which can have a comparatively tight coupling to thetransmitting oscillatory circuits, but on the contrary, as alreadystated, must be coupled comparatively loosely to the receiving circuits.

Fig. 2 shows a simplified installation which does not require specialapparatus for producing high frequency current.

By talking into the microphone we, there is produced in the oscillatorycircuit constituted by the ca acity c and the self-inductanoe l, trainso damped waves correspondd ing to the sound waves acting on the microhone.

All that has been said with reference to Fig. 1, is also applicable inthis case.

Fig. 3 shows a further improvement. It relates to an arrangement bymeans of which it is possible to use the same oscillatory circuit at onetime as a transmitter,

and another time as a receiver, so that it is possible alternately totalk and to listen with one and the same apparatus. This result isobtained owing to a commutator or switch a which switches into theoscillatory circuit, either the microphone m and the battery, or thedetector d and the telephone b.

This switch can be designed so as to allow at the same time of a changeof coupling of the self-induction coil Z with the line 7, so that whentalking, there is produced a tighter coupling, and when listening, alooser coupling. This is effected by connecting switch 8 by means of rod7" with one arm of bell crank or bent lever g, and connecting the otherarm of g by means of rod 1 with pivoted arm a, to which is attached coil1.

Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatWhat I claim is:

1. In a s stem of multiplex telephony, a plurality 0% stations havingboth transmitting and receiving apparatus, a common line circuit, meanscoupled to said line circuit for impressing electric oscillations ofdifl'erent frequencies upon said line circuit, means for modifying saidelectric oscill tions by sound waves, local circuits at each stationtuned to a particular frequencyof said electric oscillations and meansfor lacing either the transmitting or the receiving apparatus inoperative connection with the common line circuit and for simultaneouslychanging the coupling between said local circuits and the common linecircuit.

2. The combination with a conductor, of transmission means coupledthereto for impressing electric oscillations thereon, receiving meansassociated with said transmission means, and shifting means operative toplace either said transmission means or said receivin means intooperative relation to said con uctor and to simultaneously modify thecoupling between said conductor and said transmission means.

3. The combination with a conductor provided with a coil, of a coilinductively related to and movable with respect to said first mentionedcoil, transmission means for impressing electric oscillations on saidsecon mentloned coil, receiving means for receiving electricoscillations from said sec- 0nd mentioned coil and means operative toconnect either said transmission means or said receiving meansoperatively to said second mentioned coil and to vary the disstancebetween said coils as a result of such connection.

4. The combination with a conductor provided with a coil, of a coilinductively related to and movable with respect to said first mentionedcoil, transmission means including a microphone for impressing electricoscillations on said second mentioned coil, receiving means including atelephone anda detector for receiving electric oscillations from saidsecond mentioned coil, and means operative to connect either saidtransmission means or said receiving means operatively to said secondmentioned coil and to vary the distance between said coils as a resultof such connection.

5. The combination with a conductor, of means spaced from butinductively connected to said conductor, transmission means forimpressing electric oscillations on said first mentioned means,receiving means for receiving electric oscillations from said firstmentioned means, and means operative to connect either said transmissionmeans or said sreceiving means operatively to said first mentioned meansand to simultaneously and automatically vary the distance between saidconductor and said first mentioned means.

6. The combination with a conductor, of means spaced from butinductively connected to said conductor, transmission means forimpressing electric oscillations on said first mentioned means,receiving means for receiving electric oscillations from said firstmentioned means, and switching means operative to connect either saidtransmission means or said receiving means operativel to said firstmentioned means and to simu taneously and automatically va'rg' the dis-'stance between said conductor an aid first mentioned means.

In testimon whereof I aflix my signature in presence 0 two witnesses.

ERNST RUHMER. Witnesses:

WALDEMAR Ham, HENRY HAsrnn.

